Continued: After ousting party rival, new Aussie PM seeks 'kinder and gentler' politics ahead of election

Bryce revealed that she took late-night legal advice on whether she should swear in Rudd. A minority government such as Gillard led has not been seen in Australian federal politics since World War II, and Labor's leadership change raised unique constitutional questions.

While Rudd has the support of his party, Labor has just 71 seats in the 150-seat House of Representatives. Gillard was able to govern with support from some independents and the minor Greens party. They are not obligated to support Rudd, though he did get the backing of at least two independent lawmakers who had not supported Gillard.

Rudd's statement fulfilled a condition set by Bryce that he quickly notify Parliament of his appointment so that lawmakers had an opportunity to take action.

Gillard said after her loss Wednesday that she was proud of her government's achievements, including the introduction of an unpopular carbon tax paid by the biggest industrial polluters. She had been dogged by her pre-election promise never to introduce such a tax.

Gillard's gender was a focus several times during her tenure, and she made international headlines for calling Abbott a misogynist.

She said Wednesday that because of her tenure, "It will be easier for the next woman and the woman after that and the woman after that. And I'm proud of that."